An evolved packet system (EPS) includes an evolved universal mobile telecommunication system territorial access network (E-UTRAN) and an evolved packet core network (EPC). In order to support a circuit switched (CS) service, for example, a CS voice and a CS short message (SMS), in the EPS, an SGs interface is deployed between a mobility management entity (MME) of the EPS and a mobile switch center/visitor location register (MSC/VLR) of a circuit switched network to enable a user equipment (UE) to originate and receive the CS service at the EPS network, and return to a circuit domain (for example, a 2G/3G network) via an E-UTRAN, so as to complete the CS service, where the network architecture and the processing method may be referred to as “CS Fallback” (CSFB).
In the CSFB, the processing way of the short message service differs from those of other CS services (for example, the voice and the CS supplementary service). That is, the short message service does not need to fall back into the 2G/3G network. Short message delivery between the UE and the MSC/VLR is directly completed via the MME in the EPS network. Therefore, it is generally referred to as an “SMS over SGs” technology. In the prior art, the SMS over SGs processing process originated by the user (Mobile Originating SMS (MO SMS)) can achieve sending of a short message, and the SMS over SGs processing process received by the user (Mobile Terminated SMS (MT SMS)) can achieve receiving of a short message.
In the MO SMS process, when the user equipment is in an abnormal state, for example, the context of the user equipment in the MSC/VLR is lost, or the MSC/VLR cannot process the short message of the user, due to reasons such as a failure of the MSC/VLR (for example, the board reset), or the MSC/VLR recovering from a fault. At this time, the MSC/VLR indicates the MME that the current process fails, so the MME marks in the context of the UE in the MME, and indicates the UE to re-originate the registration to the MSC/VLR when the UE subsequently originates the tracking area update process. While it is not determined when the UE can originate the tracking area update process, and generally, at least several hours are needed, in this time period, the user cannot send the short message, that is, the sending of the short message cannot be achieved.
In the MT SMS process, when the user equipment is in an abnormal state, for example, the context of the user equipment in the MSC/VLR is lost, due to reasons such as a failure of the MSC/VLR (for example, the board reset), or the MSC/VLR recovering from the fault. At this time, the MSC/VLR can still receive a short message sent by an SMS-gateway mobile switching center (SMS-GMSC), and further send a paging message to the MME, and the MME further sends a service request message to the MSC/VLR, so as to indicate the MSC/VLR to start sending the short message. However, the user equipment context of the UE in the MSC/VLR is lost, so the MSC/VLR ignores the service request message sent by the MME, and cannot send the short message to the UE, that is, the receiving of a short message cannot be achieved. However, the MSC/VLR ignores the paging response sent by the MME, that is, the service request message, so the MSC/VLR considers that this paging fails, and pages repeatedly, resulting in a waste of network resources.